Active Alignment

Main objectives

Manipulating or characterizing small scale objects using robots often induces many local and influent phenomenon such as surface forces, electric fields...These effects are often considered as badly influent because they usually induce difficulties to control manipulation tasks and prevent from good positioning accuracy. The original idea of our work, is to take advantages of these phenomenon that we consider as very rich and local source of information, then feedback for control. For this reason we are developping several emebeed sensors able to directly measure phenomenon that happens at contacts and the related control scheme to suceed in achieving comple robotized tasks within environments that suffer from many influences.

Optical active alignement using micropositioning robots

As an example, we are investigating optical-based active alignement feedback to succeed in high positioning accuracy, high speed complex assembly tasks for integrated optics. Active alignement techniques usually consist in using the optical feedback from an integrated optical device during its assembly. The assembly converges when an optical signal is maximized for instance. Convergence time may be pretty long and risky because motions (done by robots or human) is not referenced in the optical frame.

To prevent from these key drawbacks, our works investigate a more synergetic may combining robot control and optical signal maximization together along a photo-robotic approach. Indeed, through modelling and experimental identification steps, we can accurately identify many parameters such as the positioning of optical components in the robot frame, many imperfections of the robot  and then can simultaneously achieve the calibration of the robot and the its control to directly, fastly and acurately maximize the optical signal.

Original integrated optical devices achitectures

For example, the assembly of an optical microscale lamella has been demonstrated with the proposed approach and less than 6 seconds are required to identiy all parameters and automatically assemble the lamella. Results obtained also demonstrated that a positioning accuracy better than 0.002° can be achieved in a repeatable way which appears more than promising.

The left hand side image above shows a SEM view of a microdisk resonator in a diced membrane. A needle and micropositioning robot is used to grip the disk. The right hand side image shows the disk that has been placed at the top of the waveguide, and the needle hole is used to bond the microdisk to the waveguide naphthalene. Such assemblies are goind to be done using active alignement techniques and will notably expect to demonstrate the influence of the position onto the optical performances of the resonator. It is notably expected to reach better performances using assembled devices than monolithic clean-room fabricated devices.

People involved

Nadège Courjal, Houari Bettahar, Florent Behague, Alexis Caspard, Jean-Yves Rauch, Roland Salut, Olivier Lehman, Philippe Lutz, Cédric Clévy

Related publications

H. Bettahar, C. Clévy, F. Behague, N. Courjal, P. Lutz, Novel Strategy for High Precision Automated Robotic Positioning based on Fabry-Perot Interferometry Principle, IEEE CASE Conference on Automation Science and Engineering, Munich, Germany, Augut 2018.

A. Caspar, F. Behague, M. Suarez, R. Salut, O. Lehmann, V. Calero, B. Robert, C. Clévy, P. Lutz, M-P. Bernal, and N. Courjal, LiNbO3 integrated microdisk resonator fabricated by optical-grade dicing and precise robotic positioning, In : Fiber Lasers and Glass Photonics: Materials through Applications. SPIE Photonics Europe, Strasbourg, France, May 2018.

H. Bettahar, A. Gaspar, C. Clévy, N. Courjal and P. Lutz, Photo-Robotic Positioning for Integrated Optics, IEEE Robotics and Automation Letters (RAL), 2(1), pp. 217-222, January 2017.